You could ask him why he thinks it fell out, he might be insulted if you seem accusatory.
When you floss, you should rub it in a shoe shining motion
around the tooth. up and down can cause food to the packed into the gum, or it can slice into your gum, but the "C
" action actually wipes stuff off the tooth and doesn't pull out dental work
Also, new amalgam (silver) fillings don't appear all that shiny or silver right away.